Shelved background drawing, plus monsters stalk the player

- Got threading to work, in Windows too. But, there's no requirement for
this, so I'm leaving it commented-out for now.
- Monsters stalk the player; they have a Moves component with a stalk
behavior.
- Removed aynch I/O (it messed up moving) and hid the cursor; added
function to set cursor position to Console
- Cleaned up build/clean scripts